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https://www.readbyqxmd.com/read/28230998/influence-of-the-anomeric-conformation-in-the-intermolecular-interactions-of-glucose
#1
Imanol Usabiaga, Jorge González, Iker León, Pedro Felipe Arnaiz, Emilio J Cocinero, Jose A Fernandez
Carbohydrates are together with amino acids, DNA bases and lipids the building blocks of living beings. They play a central role in basic functions as immunity and signaling, which are governed by non-covalent interactions between sugar units and/or with other biomolecules. To get insights on such interactions between monosaccharide units, we used a combination of mass-resolved laser spectroscopy in supersonic expansions and molecular structure calculations. The results obtained clearly demonstrate that the small stability difference between the α/β anomers of glucopyranose derivatives is reversed and amplified during molecular aggregation, making the complexes of the β-anomers significantly more stable...
February 23, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28230991/electron-accumulation-on-naphthalene-diimide-photosensitized-by-ru-2-2-bipyridine-3-2
#2
Michael Skaisgirski, Xingwei Guo, Oliver S Wenger
In a molecular triad comprised of a central naphthalene diimide (NDI) unit flanked by two [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) sensitizers, NDI(2-) is formed after irradiation with visible light in deaerated CH3CN in the presence of excess triethylamine. The mechanism for this electron accumulation involves a combination of photoinduced and thermal elementary steps. In a structurally related molecular pentad with two peripheral triarylamine (TAA) electron donors attached covalently to a central [Ru(bpy)3](2+)-NDI-[Ru(bpy)3](2+) core but no sacrificial reagents present, photoexcitation only leads to NDI(-) (and TAA(+)), whereas NDI(2-) is unattainable due to rapid electron transfer events counteracting charge accumulation...
February 23, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28230989/development-of-the-first-generation-of-disulfide-based-subtype-selective-and-potent-covalent-pyruvate-dehydrogenase-kinase-1-pdk1-inhibitors
#3
Yifu Liu, Zuoquan Xie, Dan Zhao, Jin Zhu, Fei Mao, Shuai Tang, Hui Xu, Cheng Luo, Mei-Yu Geng, Min Huang, Jian Li
Pyruvate dehydrogenase kinases (PDKs) are overexpressed in most cancer cells and are responsible for aberrant glucose metabolism. We previously described Bis(4-morpholinyl thiocarbonyl)-disulfide (JX06, 16) as the first covalent inhibitor of PDK1. Here, based on the scaffold of 16, we identify two novel types of disulfide-based PDK1 inhibitors. The most potent analog, 3a, effectively inhibits PDK1 both at the molecular (kinact/Ki = 4.17×103M-1s-1) and the cellular level (down to 0.1 μM). In contrast to 16, 3a is a potent and subtype-selective inhibitor of PDK1 with >40-fold selectivity for PDK2-4...
February 23, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28230977/extracellular-self-assembly-of-functional-and-tunable-protein-conjugates-from-bacillus-subtilis
#4
Charlie Gilbert, Mark Howarth, Colin R Harwood, Tom Ellis
The ability to stably and specifically conjugate recombinant proteins to one another is a powerful approach for engineering multifunctional enzymes, protein therapeutics and novel biological materials. While many of these applications have been illustrated through in vitro and in vivo intracellular protein conjugation methods, extracellular self-assembly of protein conjugates offers unique advantages: simplifying purification, reducing toxicity and burden, and enabling tunability. Exploiting the recently described SpyTag-SpyCatcher system, we describe here how enzymes and structural proteins can be genetically-encoded to covalently conjugate in culture media following programmable secretion from Bacillus subtilis...
February 23, 2017: ACS Synthetic Biology
https://www.readbyqxmd.com/read/28230916/design-principles-for-covalent-organic-frameworks-as-efficient-electrocatalysts-in-clean-energy-conversion-and-green-oxidizer-production
#5
Chun-Yu Lin, Lipeng Zhang, Zhenghang Zhao, Zhenhai Xia
Covalent organic frameworks (COFs), an emerging class of framework materials linked by covalent bonds, hold potential for various applications such as efficient electrocatalysts, photovoltaics, and sensors. To rationally design COF-based electrocatalysts for oxygen reduction and evolution reactions in fuel cells and metal-air batteries, activity descriptors, derived from orbital energy and bonding structures, are identified with the first-principle calculations for the COFs, which correlate COF structures with their catalytic activities...
February 23, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28229499/advanced-materials-for-use-in-soft-self-healing-devices
#6
REVIEW
Tan-Phat Huynh, Prashant Sonar, Hossam Haick
Devices integrated with self-healing ability can benefit from long-term use as well as enhanced reliability, maintenance and durability. This progress report reviews the developments in the field of self-healing polymers/composites and wearable devices thereof. One part of the progress report presents and discusses several aspects of the self-healing materials chemistry (from non-covalent to reversible covalent-based mechanisms), as well as the required main approaches used for functionalizing the composites to enhance their electrical conductivity, magnetic, dielectric, electroactive and/or photoactive properties...
February 23, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28229141/functionalized-diamond-nanothreads-from-benzene-derivatives
#7
J F R V Silveira, A R Muniz
Diamond nanothreads (DNTs) are fully sp(3)-bonded one-dimensional carbon nanostructures, synthesized recently through compression of crystalline benzene. They possess outstanding mechanical strength, suitable for the development of novel nanostructured reinforced materials. In this article, we use density functional theory calculations to investigate the feasibility and physical properties of functionalized DNTs. We show that the stacking and covalent bonding of benzene derivative molecules (toluene, aniline, phenol and fluorobenzene) may lead to stable configurations analogous to benzene-derived DNTs, with functional groups (-CH3, -NH2, -OH, -F) covalently attached to the surface...
February 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28228478/an-engineered-tgf-%C3%AE-monomer-that-functions-as-a-dominant-negative-to-block-tgf-%C3%AE-signaling
#8
Sun Kyung Kim, Lindsey Barron, Cynthia S Hinck, Elyse M Petrunak, Kristin E Cano, Avinash Thangirala, Brian Iskra, Molly Brothers, Machell Vonberg, Belinda Leal, Blair Richter, Ravindra Kodali, Alex B Taylor, Shoucheng Du, Christopher O Barnes, Traian Sulea, Guillermo Calero, P John Hart, Matthew J Hart, Borries Demeler, Andrew P Hinck
The transforming growth factor beta isoforms, TGF-β1, -β2, and -β3 are small secreted homodimeric signaling proteins with essential roles in regulating the adaptive immune system and maintaining the extracellular matrix. However, dysregulation of the TGF-β pathway is responsible for promoting the progression of several human diseases, including cancer and fibrosis. In spite of the known importance of TGF-βs in promoting disease progression, no inhibitors have been approved for use in humans. Herein, we describe an engineered TGF-β monomer, lacking the heel helix, a structural motif essential for binding the TGF-β type I receptor, TβRI, but dispensible for binding the other receptor required for TGF-β signaling, the TGF-β type II receptor, TβRII, as an alternative therapeutic modality for blocking TGF-β signaling in humans...
February 22, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28228066/dynamic-protein-s-palmitoylation-mediates-parasite-life-cycle-progression-and-diverse-mechanisms-of-virulence
#9
Robert W B Brown, Aabha I Sharma, David M Engman
Eukaryotic parasites possess complex life cycles and utilize an assortment of molecular mechanisms to overcome physical barriers, suppress and/or bypass the host immune response, including invading host cells where they can replicate in a protected intracellular niche. Protein S-palmitoylation is a dynamic post-translational modification in which the fatty acid palmitate is covalently linked to cysteine residues on proteins by the enzyme palmitoyl acyltransferase (PAT) and can be removed by lysosomal palmitoyl-protein thioesterase (PPT) or cytosolic acyl-protein thioesterase (APT)...
April 2017: Critical Reviews in Biochemistry and Molecular Biology
https://www.readbyqxmd.com/read/28225628/insights-into-the-diels-alder-reaction-between-3-vinylindoles-and-methyleneindolinone-without-and-with-the-assistance-of-hydrogen-bonding-catalyst-bisthiourea-mechanism-origin-of-stereoselectivity-role-of-catalyst
#10
Chao-Xian Yan, Fan Yang, Xing Yang, Da-Gang Zhou, Pan-Pan Zhou
The Diels-Alder reaction between 3-vinylindoles and methyleneindolinone can proceed both with catalyst-free and bisthiourea catalyst, the reaction with bisthiourea is much faster and yields product with even higher stereoselectivity. The reaction mechanisms, origin of stereoselectivity and role of catalyst were elaborated based on quantum mechanical calculations and theoretical methods of reactivity indexes, NCI, QTAIM and distortion/interaction models. In uncatalyzed reaction, the two C-C bonds formed undergo the conversion from noncovalent to covalent bonding via concerted asynchronous mechanism...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28225620/solvent-independent-anharmonicity-for-carbonyl-oscillators
#11
Samuel Hayes Schneider, Huong T Kratochvil, Martin T Zanni, Steven G Boxer
The physical origins of vibrational frequency shifts have been extensively studied in order to understand non-covalent intermolecular interactions in the condensed phase. In the case of carbonyls, vibrational solvatochromism, MD simulations, and vibrational Stark spectroscopy suggest that the frequency shifts observed in simple solvents arises predominately from the environment's electric field due to the vibrational Stark effect. This is contrary to many previously invoked descriptions of vibrational frequency shifts, such as bond polarization, whereby the bond's force constant and/or partial nuclear charges are altered due to the environment, often illustrated in terms of favored resonance structures...
February 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28225356/improving-mechanical-properties-of-carbon-nanotube-fibers-through-simultaneous-solid-state-cycloaddition-and-crosslinking
#12
Nam-Goo Kang, Xinyi Lu, Nitilaksha Hiremath, Kunlun Hong, Maria Evora, Victoria Ranson, Amit Naskar, Gajanan Bhat, Jimmy Mays
Individual carbon nanotubes (CNTs) exhibit exceptional mechanical properties. However, difficulties remain to fully realize these properties in CNT macro-assemblies, because of the sliding past one another resulting from the weak inter-tube forces. Herein, a simple solid-state reaction is presented that enhances the mechanical properties of carbon nanotube fibers (CNTFs) through simultaneous covalent functionalization and crosslinking. This is the first chemical crosslinking proposed without involvement of catalyst or byproducts...
February 22, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28225269/indazole-based-covalent-inhibitors-to-target-drug-resistant-epidermal-growth-factor-receptor
#13
Stefano Tomassi, Jonas Lategahn, Julian Engel, Marina Keul, Hannah Lea Tumbrink, Julia Ketzer, Thomas Mühlenberg, Matthias Baumann, Carsten Schultz-Fademrecht, Sebastian Bauer, Daniel Rauh
The specific targeting of oncogenic mutant epidermal growth factor receptor (EGFR) is a breakthrough in targeted cancer therapy and marks a drastic change in the treatment of non-small cell lung cancer (NSCLC). The recurrent emergence of resistance to these targeted drugs requires the development of novel chemical entities that efficiently inhibit drug-resistant EGFR. Herein, we report the optimization process for a hit compound that has emerged from a phenotypic screen resulting in indazole-based compounds...
February 22, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28225253/glutathione-adduct-patterns-of-michael-acceptor-carbonyls
#14
Christian Slawik, Christiane Rickmeyer, Martin Brehm, Alexander Böhme, Gerrit Schüürmann
Glutathione (GSH) has so far been considered to facilitate detoxification of soft organic electrophiles through covalent binding at its cysteine (Cys) thiol group, followed by stepwise catalyzed degradation and eventual elimination along the mercapturic acid pathway. Here we show that in contrast to expectation from HSAB theory, Michael-acceptor ketones, aldehydes and esters may form also single, double and triple adducts with GSH involving β-carbon attack at the much harder N-terminus of the γ-glutamyl (Glu) unit of GSH...
February 22, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28225218/synthesis-of-n-n-dialkylamino-nor-dihydroxanthene-hemicyanine-fused-near-infrared-fluorophores-and-their-first-water-soluble-and-or-bioconjugatable-analogues
#15
Jean-Alexandre Richard, Michelle Jui Hsien Ong, Sylvain Debieu, Mathieu Moreau, Anthony Romieu
The effective synthesis of extended conjugated N,N-dialkylamino-nor-dihydroxanthene-based fluorophores is described from diversely functionalized salicylic aldehydes. The access to these original fluorescent derivatives proceeded in two steps through a one-pot construction of the unusual nor-dihydroxanthene (nor-DHX) scaffold followed by a diversification step providing a wide variety of nor-DHX-hemicyanine fused dyes emitting in the range 730-790 nm. The versatility of our approach has enabled a further extension to the late-stage introduction of negatively/positively charged polar groups onto their terminal nitrogen heterocyclic subunit giving access to the first water-soluble and/or bioconjugatable members of this emerging class of NIR fluorophores...
February 22, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28225177/an-irreversible-inhibitor-of-hsp72-that-unexpectedly-targets-lysine-56
#16
Jonathan Pettinger, Yann-Vaï Le Bihan, Marcella Widya, Rob L M van Montfort, Keith Jones, Matthew D Cheeseman
The stress-inducible molecular chaperone, HSP72, is an important therapeutic target in oncology, but inhibiting this protein with small molecules has proven particularly challenging. Validating HSP72 inhibitors in cells is difficult owing to competition with the high affinity and abundance of its endogenous nucleotide substrates. We hypothesized this could be overcome using a cysteine-targeted irreversible inhibitor. Using rational design, we adapted a validated 8-N-benzyladenosine ligand for covalent bond formation and confirmed targeted irreversible inhibition...
February 22, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28225169/a-polyaromatic-molecular-clip-that-enables-the-binding-of-planar-tubular-and-dendritic-compounds
#17
Keisuke Jono, Akira Suzuki, Munetaka Akita, Ken Albrecht, Kimihisa Yamamoto, Michito Yoshizawa
By the covalent linkage of two bent bisanthracene amphiphiles with a biphenyl spacer bearing hydrophilic pendants, we synthesized a new molecular clip with a C-shaped conformation. The molecular clip provides an acyclic, open cavity surrounded by four anthracene panels in water. In contrast to previous clip- and tweezers-like compounds as well as cage-shaped compounds, the C-shaped polyaromatic cavity displays unusual wide-ranging capturing abilities toward not only planar perylene-based pigments and cylindrical single-walled carbon nanotubes but also highly branched macromolecules (carbazole dendrimers)...
February 22, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28225090/proton-transfer-dynamics-dictate-quinone-speciation-at-lipid-modified-electrodes
#18
Edmund C M Tse, Christopher J Barile, Ying Li, Steven C Zimmerman, Ali Hosseini, Andrew A Gewirth
Proton-coupled electron transfer (PCET) reactions are ubiquitous in biochemistry and alternative energy schemes. Natural enzymes utilize quinones in proton transfer chains and energy conversion processes. Here, we utilize a bio-inspired hybrid bilayer membrane system to control the reaction mechanism of a quinone molecule covalently bound to an electrode surface. In particular, by impeding proton access to the quinone moiety, we change the reaction pathway from a PCET process to a pure electron transfer step...
February 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28225039/ruthenium-based-metallopolymer-grafted-reduced-graphene-oxide-as-a-new-hybrid-solar-light-harvester-in-polymer-solar-cells
#19
R Vinoth, S Ganesh Babu, Vishal Bharti, V Gupta, M Navaneethan, S Venkataprasad Bhat, C Muthamizhchelvan, Praveen C Ramamurthy, Chhavi Sharma, Dinesh K Aswal, Yasuhiro Hayakawa, B Neppolian
A new class of pyridyl benzimdazole based Ru complex decorated polyaniline assembly (PANI-Ru) was covalently grafted onto reduced graphene oxide sheets (rGO) via covalent functionalization approach. The covalent attachment of PANI-Ru with rGO was confirmed from XPS analysis and Raman spectroscopy. The chemical bonding between PANI-Ru and rGO induced the electron transfer from Ru complex to rGO via backbone of the conjugated PANI chain. The resultant hybrid metallopolymer assembly was successfully demonstrated as an electron donor in bulk heterojunction polymer solar cells (PSCs)...
February 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28224898/non-covalently-crosslinked-chitosan-nanofibrous-mats-prepared-by-electrospinning-as-substrates-for-soft-tissue-regeneration
#20
Chiara Tonda-Turo, Francesca Ruini, Martina Ramella, Francesca Boccafoschi, Piergiorgio Gentile, Emilia Gioffredi, Giuseppe Falvo D'Urso Labate, Gianluca Ciardelli
Chitosan (CS) membranes obtained by electrospinning are potentially ideal substrates for soft tissue engineering as they combine the excellent biological properties of CS with the extracellular matrix (ECM)-like structure of nanofibrous mats. However, the high amount of acid solvents required to spun CS solutions interferes with the biocompatibility of CS fibres. To overcome this limitation, novel CS based solutions were investigated in this work. Low amount of acidic acid (0.5M) was used and dibasic sodium phosphate (DSP) was introduced as ionic crosslinker to improve nanofibres water stability and to neutralize the acidic pH of electrospun membranes after fibres soaking in biological fluids...
April 15, 2017: Carbohydrate Polymers
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